Trypsin was treated by high pressure technology,and its spatial structure was changed,the relationship between structural changes and trypsin activity was investigated.The secondary structure change of trypsin after pressure treatment was observed by Fourier transform infrared spectroscopy(FTIR).Moreover its tertiary structure change was observed by fluorescence spectroscopy;and its activity was tested using Folin phenol method.The results showed that,compared with the untreated(0.1 MPa),trypsin activity change was significant(p<0.05) under different pressure(100～600 MPa) treatment at 37 ℃ for 20 min.After treated with 300 MPa,its activity was 0.386 times higher than the untreated.Secondary structure of trypsin was analysed using FTIR,and the peak area ratio of α-helix and β-turn in secondary structure was the maximum(2.749);Endogenous fluorescence spectra intensity was the maximum(1 353) at excitation wavelength 295 nm,and was 4 262 at excitation wavelength 280 nm;exogenous fluorescent spectra intensity was 2 022 at excitation wavelength 228 nm,all these change was remarkable(p<0.05)comparing with the untreated.Therefore,ultrahigh pressure processing influence on the spatial structure of trypsin and induce enzyme activity change.Trypsin activity is relate to the peak area ratio of α-helix and β-turn and the exposure degree of Trp and other hydrophobic a mino acid residues and Tyr.